In optical measuring apparatuses it may often be important to carry out a reference measurement in relation to an actual measurement. The reference measurement can be used for the purpose of calibrating the measuring apparatus.
By way of example, apparatus-internal reference sections can be provided for carrying out the reference measurement. DE 10 2005 037 253 A1 discloses e.g. a distance measuring apparatus with a reference section.
The reference measurement can be carried out before, after or simultaneously with the actual measurement. In the case of simultaneous measurement, it is possible for measurement radiation to pass to the receiver for reference radiation and for reference radiation to pass to the receiver for measurement radiation. This crosstalk considerably reduces the measurement accuracy. The crosstalk can be all the more intensive, the closer together the receivers for reference radiation and measurement radiation are arranged.